To reduce overheating on an engine and related components, a cooling system may route coolant through a single cooling circuit that includes the engine and a radiator or other heat exchanger. The temperature of the engine may be regulated in part by adjusting the speed of one or more cooling system fans to adjust an amount of cooling of the coolant within the single cooling circuit. However, the temperature of coolant provided to the engine in a single circuit system may be too cool to maintain a designated operating temperature of the engine. Further, the temperature of coolant provided to other heat exchangers in the single circuit may be too warm to maintain a designated operating temperature for respective elements of the cooling system that are cooled by the other heat exchangers.